Storage system



AT TQBLVEV INVENTOR Rf. SME/LER @Lum Sept- 3, 1963 R. E. sTAr-:HLER

STORAGE SYSTEM Filed June 5, 1959 Z A m33? w United States Patent() Filed .lune 5, 1959, Ser. No. 818,410 7 Claims. (Ci. 340-173) t* This invention relates to infomation storage systems and more particularly to systems for temporary and relatively permanent storage of large quantities of informa.

tion.

Various applications, including telephone communication systems and computers in general, require the storage of a large quantity of information, a portion of which is changed at frequent intervals and the balance of which is rarely changed. l

Fll'ne relatively permanent storage of large amounts of information may be accomplished by employment of a system termed the Flying Spot Store, as disclosed `in Patent 2,830,285, issuedl to R. C. Davis and myself on f April 8, 1958, and in an article entitled Fundamental Concepts in the Design of the 'Flying Spot Store, by C. W. Hoover, lr., R. E. Staehler, Iand R. W. Ketchledge, appearing in the Bell System Technical Journal, vol. 37, No. 5, September 1958, pages 116l-1194. In this system Vinformation` is stored on minute, discrete areas of a storage surface such as a photographic slide. Light emanating from the luminescent surface of a cathode 'ray tube, due to selective deflection of an electron beam to ,impinge a particular position on the tube surface, is focused on a desiredy discrete area `of the slide. The response from photocellsA positioned to receive light from the screen i through the slide indicates the `information stored at the selected discrete area.

`'Ilhe principal diiiiculty encountered in such a system, Which is overcome lin accordance with the cited Davis et al. patent, is rapid and accurate yaccess to and readout of information from a highly concentrated information storage surface. Such operation necessarily requires employment of precise and reliableinitial-aocess and beam deliection correction circuitry.

Temporary information storage may be accomplished,

by employment of any of aivariety of storage devices including the vbarrier grid storage tube of the type dis# closed, for example, in M. E. Hines Patent 2,844,722,

issued July 22, 1958. In` the barrier grid tube, information is stored as discrete areas of charge at a dielectric target and is destroyed in the readout process which includes deiiecting an electron beam to impinge the selected storage area. Again, rapid and accurate access .to the `storage area is of paramount importance. Beam positioning circuitry, suoh as that disclosed in C. Ault application Serial No. 631,554, filed December 31, 1956, now Patent No. 2,904,721, issued September 15, 1959, is required to assure continued accuracy of information storage and readout in the event that the input address circuitry fails to maintain exact bea-m positioning for relatively long periods of time.

` Thus a system utilizing both temporary and permanent storage units, such as the telephone system disclosed, for example, in Budlong-DreW-Harr patent application Serial No. 688,386, led October 7, 1957, now Patent No. 2,955,165, issued October4, 1960, demands` access and error correction circuitry for each type ofstorage unit. Independent circuitry (for each component, as disclosed in the Budlong et al. patent, necessarily increases system initial cost, and in relatively small operations, such as a telephone cnice servingyon the order o f 10010 subscriber lines, this expense is a considerable factor in determining adoption of such La system.

`temporary and semi-permanent storage units;

.store is obviated.

It is an object of this invention to provide an improved information storage system. l

It is `another object `of this invention to `provide an improved combined temporary and permanent information storage system with a minimum of ancillary components. p

lt is a further object of this invention to realize'precise, monitoring of the electron beam in the reading operation of the temporary information storage unit and to improve the speed and `accuracy of beam positioncrdeection error correction.

lt is a still `further object of this invention to provide an economical time-shared temporary yand permanent infonmationstorage system.

`These and other objects of my invention are' attained `in accordance with one specilic illustrative embodiment thereof :by a unique system arrangement and manner of operation which permit the compatible combination of access and beam deilection correction circuitry for the Hereinafter, an electron beam storage unit such as the Flying Spot Store, whichis designed to provide semi-permanent information storage, will be referred to as the permanent store-and reference to the temporary store will connote electron Abeam storage units designed to permit frequent change of `stored information, `such as the barrier [grid tube store. i

. Generally speaking, `the beam deflection circuitry utilidad in initial `access to particular information in the permanent store Vis comparable to that employed in initial access to information in the temporary store. In `addition, the problems encountered in assuring accurate positioning of the electron beam so as to impinge a desired discrete information storage area, are closely related in permanent and temporary stores. ln each instance, elements are provided whichy determine Whether or not the position of an electron beam in relation to a xed target surface is proper. The resultant of such `a dei termination is applied to the deiiection circuitry so as to reposition the electron beam. i f

In accordance with this embodiment lof my invention, initial beam dellection circuitry is connected in common to the temporary and permanent stores so as to deflect the electron beams in both stores simultaneously. In addition, the beam deflection correction circuitry'for the permanent store is connected so ras to perform the necessary positioning operation in the temporary store as Well. In this fashion, the: need `for complex and costly independent beam positioning circuitry for the temporary In accordance with one aspect of this embodiment of my invention, the flexibility of the system. is increased by time-sharing the use of the temporary and permanent stores. Such a time-sharing is facilitated by properly synchronized program-ing of the address and output circuitry in the temporary and permanent stores.

It is, therefore, a feature of this invention that a combined temporary and permanent information storage system have a common initial information address system. Y It i-s a more specific feature in accordance with one embodiment of this invention that the temporaryfand permanent stores each comprise an electron discharge,

device and a common beam deflection control system.

lIt is another feature of this invention that alcomlbined temporary and permanent information storage system con- -tain a common beam position or deflection errorcorrecand means for comparing information as` to the detected Patented Sept.` `3, 1963`f 3 l beam position with the initial beam positioning information and applying the resultant of such comparison to the ycommon beam deilection control circuitry.

It is a further feature of this invention that input information be applied to the permanent and `temporary stores concurrently and that information be vderived from each type .of store lalternatively in accordance with the particular store to which the input information is directed. A complete understanding of my invention andof these and other features thereof may be gained from consideration of the following detailed description and the accompanying drawing, the sole FIGURE of which is a system representation, mainly in block diagram form, of one specic illustrative embodiment of this invention.

s depicted in the drawing, the system contains a permanent store and a temporary store, the operations of which are directed Iby a common control 40. The common control 40 is a universal information processing center,

the operation of which is disclosed, for example, in the vaforementioned Budlong et al. patent. Under orders Ifrom.

thepermanent store, the common contr-ol 40 serves to process, on a timedivision basis, all of the actions necessary tothe operation of a complex switching system such as a telephone system. Signals from the common control 40 serve to address the permanent store to locate and read out desired information. Such information is .returned to common control and serves to direct its subsequent actions. r

lIncluded in this information are orders Ifor operation of the temporary store. The signals from the common control to the temporary store include an address and an order. The address locates the desired stored information, and the order indicates the action to be taken at the addressed storagelccation. In response to receipt of sighals, vthe temporary store indicates to common control 40 the state of the addressed location, whereupon common control 40, pursuant to orders, directs the revision or regenerationof the priorly stored information.

The permanent store, as described'in detail in the aforementioned Davis et al. patent, includes a cathode ray tube, shown -generally at 10, comprising an evacuated enclosing vesse111 having at one end an electron gun 12. The elechereinafter.

tron gun 12 produces a concentrated electron beam which is projected centrally between two pairs of deflection plates 13 and l14, mounted in space quadrature.

The electron beam is projected against a target surface 15 whichforms the face of the cathode ray tube 10 and is coated with a luminescent material. The deflection plates 13 and y14, which are energized from horizontal and vextical'deliection circuits through amplifiers 20 and 21, respectively, serve to deilect the electron beam to a desired discrete area of surface 15. The horizontal deflection circuitry is identical to the circuitry for vertical deiiection,

so that a description of the horizontal circuitry will suiiice to describe fthe structure and operation of this specic embodiment of my invention.

An input address comprising, in thi-s specific embodiment, groups of signals representing digits of a conventional binary number code, are applied in parallel form to the horizontal input regi-ster 18 which may comprise a series of bistable Hip-flop units, as known in the art,

arranged4 to provide corresponding inputs to the comparivson `circuit 35 and the analog converter 19. Such input circuitry is indicated in the -aforementioned Davis et al. patent.A Each signal in the group of input signals is converted into ananalog representation of a binary digit in `the analog converter 19, and the summation of the analogrepresentations is amplified by summing amplifier Z0 andapplied to the horizontal deilection platesl. Each discrete potential Iapplied between deflection plates 13 is intended to deflect the electron beam to impinge an area of the screen 15 corresponding to the horizontal input address;`

' The electron beam produces a spot of light at the discrete. area of the luminescent surface 15 to which it is tem 23 is positioned behind the surface 15 so as to focus the resultant light on a plurality of slides such as 24 through 29. Any number and arrangement of slides may be utilized so long as it is consistent with focusing requirements and output connections from appropriate light detection means associated with the slides. The slides contain binary information stored at discrete areas thereof which is identified by distinct light transmission characteristics. l

With the light beam focused on a discrete location of each of the slides 24-29 indicated in the drawing, light passing through these discrete locations will be focused by converging lenses 30 upon appropriate light sensitive devicesA 31 individual to each of the slides. devices may eachycomprise a phototube and amplifier, arrangement as known in the art. Light received by cer tain of the devi-ces 3-1 is transformed into electrical impulses which are delivered to the output circuitry. Such output circuitry may comprise logic lgates 37 selectively" controlled by the input circuitry to store informationin output storage rneans such as outputregister 39. I

Others of the kdevices 31 transmit impulses to repositioning circuitry for both the permanent and temporary stores. Thus infomation taken from .permanent store deilecrtion error detection slides, such as 28 and 29, isV

utilized to yrepositionthe electron beam in the permanent store` and in each of the 'temporary stores, as described tection slides Z8 and 29 is transmitted to the comparison circuit 35. v The comparison circuit, an example of which is disclosed in the aforementioned Davis et al. patent, compares the -binarycoded information thus'received with the binary coded information from the horizontal input register `18 whichserved initially to deflect the electron beam of the` cathode ray tube 10. The comparison resultant, if any,vis'transmitted to the horizontal in conjunction with control of the input address information such that output information willy be derived from the permanent store only upon receipt of pertinent address information by the permanent store.

rThe temporary store in this 4specific illustrative embodiment of my invention consists of one or more barrier grid tubes such as tube 50. 'Ilhe barrier grid tube structure is well known in lthe art, as disclosed, for example, in the aforementioned Hines patent. vantageously may'comprise within an evacuated envelope an electron gun 5.1, a beam blanking"l electrode 52, propriate accelerating and focusing electrodes: defining an electron lens 53, deection plates 54 and 55, mounted in space quadrature, and a target assembly 56. target assembly 56 includes a backplate 57, a dielectric sheet 58, and a barrier grid 59.

In destructive readout storage devices ofy this type, information is stored or written by an electrostatic charge on a discrete area of Such a charge may be placed on the surface by deiiection of the electron beam to the desired' discrete area, While the `b ackplate 5-7 is temporarily raised to a positive potential. This temporarily raises the potential of the front face of they dielectric through capacitive action. The electron beam then charges this surface with nega'- tive electrons sufiicient to drop its potential to that of the barrier grid 59; which is the equilibrium potential. When the beam is turned elsewhere and fthe backplate potential returned to normal, the charge-remains on the discrete The latter information from the deflection error de- The tube 50 adt The',

the surface of the dielectric 58.

area, leaving that portion of the dielectric surface at a negative potential.

The information `thus stored or written in this discrete` area on the surface of the dielectric 58 may be read out subsequently by returning the electron beam to Ithis discrete area. The beam, in striking the dielectric, releases more secondary electrons from the surface than there areprimary electrons stniking it, and these secondary electrons are repelled from the surface, causing the potential at the discrete area to rise to that of the barrier gnid.Y At equilibrium, the dielectric surface releases as many electrons as` `arrive and remains at the barrier grid potential. 'Ihus,`when infomation is beingread out, the

surface of the dielectric is being discharged, thereby providing a destructive readout, temporary storage operation.

It should be appreciated that any inaccuracies existing in the positioning of the electron beam on a particular discrete area of the target surface from which it is desited to obtain information, would destroy the accuracy of information read out of the temporary store. the components present in the input address circuitry are numerous and complex, such inaccuracies often may be encountered. It is essential, therefore, that a positioning system which prevents the occurrence of such inaccuracies be provided. Y

. 'Ihe structureof the barrier grid tube and its destrucftive readout operation are not compatible with a seif contained, beam deiieotion correction scheme, as employed in the permanent store. Rather, beam deflection correction schemes for temporary stores, as known in the lart and as disclosed, for example, in the aforementioned Ault patent, involve the use of additional cathode ray tubes and associated circuitry, which serve soiely as the positioning system for vthe corresponding temporary storage tubes. y.

In accordance with my invention, the need for individual temporary store positioning circuitry is obviated by the combination of the temporary store with the permanent store such that the permanent store itself serves as the positioning system for the temporary store. Thus the interconnection of the beam deflection systems for the permanent store 'and the temporary store permits the application of beam deflection correction signals, as

developed in the permanent store, for detiection correc` tion of the electron beam in the temporary store.

In conjunctionv with such an interconnection of detlection systems for the permanent `and temporary stores, access to the stores and readout of infomation therefrom, advantageously may be programed in common control 40 so as toI operate on a time division basis. Thus the stores may be interrogated alternative-ly, dependent upon the particuiar operation that the system is required to implement. Consider, for example, that a particular operation requires frequent 4access to information in the permanent store and only occasional access to the information in Ithe temporary store. AIn in'- stance, the information applied to the input registers such as 18 most frequently would be directed to readout of information from the permanent store. Coordinated with the appiication of such input address information would be the operation of the output gates such as I37 so as to assure proper readout solely lfrom the permanent store.

The electron beams in the temporary store are likewise positioned by the information inserted to position the beam in the permanent store. However, the control circuitry may be prognamed such that particuiar circuitry designed for readout from the temporary sto-re will not be enabled at this time.

Peculiar to the operation of the barrier grid tube illustrated as the temporary store in this embodiment of the invention, is the fact that destruction of the information stored at its target surface results only from positioning 6 t of the electron beam on a discrete area of the targetmember during a` reading operation. The system advantagcously may be programed such that during an intera val assigned to readout from the permanent store, the' ner due to the parallel connected deiiection systems, but

the programing is such that the permanent store output gates 37 are not enabled at this time and thus no readout from the permanent store is provided. Contrarily, the output circuitry for the temporary store is energized c0-` incident with the positioning of the beam in each tube on the discrete area of the target surface from which it is desired to obtain information.

AOne type of readout operation in the barrier grid tube is referred to as backplate reading and is illustrated in the drawing and described in detail in the aforementioned Hines patent. Briefly, the circuitry for accomplishing backplate reading in each tube 56 comprises a coaxial lin'ehaving the `inner conductor connected to the backplate 57 and the outer conductor connected to the barrier grid 59. A coiled [portion 61` of the coaxial line advantageously acts as a noninductive winding in the presence of backplate charging current, which current is applied from a source 68 connected between the inner and outer conductors of the coaxial line. An output signal, indicated by currentflow in the same direction in both of the coaxial line conductors, encounters a high impedance in the inductive winding 61, andthe ensuing voltage drop is registered in an output circuit through output ampiier the corresponding barrier grid tube 5t) is applied through.`

gate 64 to` beam control source 69. A bias potential normally is appliedto the grid 52 in each tube SG to blank the corresponding beam. Thus the signal on lead 63 to the source `69 serves to inhibit the application of the beam blanking potential from 'the source 69. The result is the focusing of the electron beam on the selected discrete area of the dielectric 58 at which information is to be written. Simultaneously, the signal on WRITE lead `63 is applied to backplate drive source 68 to permit the application of a signal from source 68`through the inductance V61 to charge the baekplate 57 to a positive potential. An output signal may be developed during the writing operation but such a signal would be relatively small in relation to a proper readout signal, such that lappropriate output circuitry would readily distinguish between them.

With the proper information written inthe selected discrete area, the electron beam in the selec-ted temporary store is removed and is lonly returned to this particular discrete `area when it 'is vdesired to read out the stored information. Considering that at some later time such readout is desired, the common control 40 will provide an input address which will serve t`o deflect the electron beams in each of the permanent and temporary storage devices tothe particular position corresponding to the desired discrete area `in the selected barrier grid tube 50. Simulatneously, a signal isvapplied to the READ input orderlea-d `67. This signal is directed through `'gate 64 and serves ttounblank the beam inthe selected tube ASt). The signal on the READ lead, however, does not permit alteration of the backplate potential. The ensuing current flow in the coaxial line of the selected tube `Sti' will produce the desired output signal through the amplifier 62. Upon readout of the information, the discrete area of the area orto write in new information ias desired. The

common control 40 provides for such a cyclic operation in which a reading yoperation is followed by a writing operation at the same discrete area prior to the next reading operation.

The speed lof system operation may be set -according to the requirements of each type of store. This is possible in that alternative operations are performed, andthe speed for each operation may be unique to the particular store being interrogated. 'Ihecapacity of the store may be varied to suit the requirements of any particular operation. Thus, if more permanent information storage is required, an increase in the information storage slides such as 26 and 27, with a corresponding increase in light sensitive devices 30 and '.Thus, considering N permanent information `channels and additional temporary information channels, and

considering 256x256 or 65,000 possible beam deflection address positions in the permanent store, andA 128 1128 or 16,000 possible addresses in each tube of the temporary store, the total capacity of the system would be 65N 103 bits of permanent information and 16n l03 bits of temporary information. v v

Another aspect of this embodiment of my invention 'worthy of consideration here is the ready adaptability of the system to interrelated information storage. The permamentl store inherently requires actual replacement of information storage slides when it is necessary to alter. a portion or'all of its content. Since the purpose offsuch a store is to develop information requiring relatively infrequent change, such a replacement is not a great burden, but it nevertheless exists. This burden may be reduced by permitting the temporary store to operate concurrently with the permanent store to provide a small portion of the otherwise permanent information.

The circuitry indicated in the drawing is readily adaptable to such operation by permitting concurrent enablement of the output circuitry in both stores and use of the output information in proper sequence. Thus the permanent store may be processed to store that portion of the information which is essentially permanent, and the few bits of a message which may require change over a period of time are stored in the temporary store where the change is readily implemented when required. The system is then operated so as to provide concurrent readout from each type of store. Since the temporary store would be required to store only a few bits of the other- A `wise permanently stored message, the respective large land small storage capacities of the permanent and temporary stores are utilized to optimum advantage.

It is to be understood that the above-described arrangements are illustrative of the application of the principles ofthe invention. Numerous other arrangements may be devised by those skilled in the art without departing from the spirit and scope of the invention.

What is claimed is:

\1. An vinformation storage system comprising a permanent store-including a cathode ray ltube having aluminescent surface, means for projecting an electron beam against said surface to produce a Ispot of`light thereat, iirst beam deflection means, an information storage medium, |and light sensitive means positioned to receive light 8 from ,said surface through said storage medium, a temporary store comprising a cathode ray tube having an informationstorage target,means forprojecting an elecvtron beam against said target, second beam deflection means and means for detecting output signals from said target, access circuitry-,connected in common ito each of said stores, means for applying input information to, said access circuitry to initiate concurrent operation-of each of said stores, distinct output circuitry kconnected Vto each corresponding store, and means for4 enabling. said permanent and temporary stores alternatively.- t

2. An Ainformation storage system in accordance with claim 1 wherein said access circuitry comprises input information register means and. comparison circuit means connected between said register means and said rst and second beam' deflection means. j

3. An information storage system in accordanceewith claim 2 and further comprising beam deflection correction means positioned to receive light from said cathode ray tube surface through said information` storage medium, and means for applyingelectrical signals from said` beam deflection correction means to said comparison cir-` meansl for connecting saidvoutput circuitry to said input information applying means for enabling alternatively said temporary and permanentstoreoutput circuitry upon deflectionv of the electron beams infeach of said stores to the position specified by said input information.

5. A storage ysystem comprising a first electron dis'- charge device having an information storage target, means for projecting an'electron'beamv against said target, a second electron discharge device having a luminescent surface, means for projecting an electron beam against said surface, a plurality of information storage and error correcting'members' positioned in front of said luminescent surface, light responsive means for generating electrical signals in response to light transmitted thereto! from said luminescent surface through said error correcting members, common means for deflecting concurrently the beams in' said first and second electron discharge devices, and means for applying said electrical signals to said common beam deflecting means.

6.- A storage system in accordance with claim 5 wherein said common beam deilecting means comprises means .for registering input information tor address the electron beams in said devices, comparison means connected be. tween said register means and said light responsive means for comparing the electrical signals from said light responsivemeans with the input information in said regisv ter means, and means for applying the comparison resultant from said comparison means in common to the beam deflection elements in said first and second devices.

7. A storage system in accordance with claim 6 and further comprising distinct output means associated with Y 2,457,911 Munster Jan. 4, 1949 2,702,356 Flory Feb. 15, 1955 2,830,285 'Davis et al. p f Apr. 8,'1958 2,853,695 Chu` l V 7.--- Sept. 23, 1958 FOREIGN' PATENTS Y y l 524,673

Canada 1 l May 1, 1956 

1. AN INFORMATION STORAGE SYSTEM COMPRISING A PERMANENT STORE INCLUDING A CATHODE RAY TUBE HAVING A LUMINESCENT SURFACE, MEANS FOR PROJECTING AN ELECTRON BEAM AGAINST SAID SURFACE TO PRODUCE A SPOT OF LIGHT THEREAT, FIRST BEAM DEFLECTION MEANS, AN INFORMATION STORAGE MEDIUM, AND LIGHT SENSITIVE MEANS POSITIONED TO RECEIVE LIGHT FROM SAID SURFACE THROUGH SAID STORAGE MEDIUM, A TEMPORARY STORE COMPRISING A CATHODE RAY TUBE HAVING AN INFORMATION STORAGE TARGET, MEANS FOR PROJECTING AN ELECTRON BEAM AGAINST SAID TARGET, SECOND BEAM DEFLECTION MEANS AND MEANS FOR DETECTING OUTPUT SIGNALS FROM SAID TARGET, ACCESS CIRCUITRY CONNECTED IN COMMON TO EACH OF SAID STORES, MEANS FOR APPLYING INPUT INFORMATION TO SAID ACCESS CIRCUITRY TO INITIATE CONCURRENT OPERATION OF EACH OF SAID STORES, DISTINCT OUTPUT CIRCUITRY CONNECTED TO EACH CORRESPONDING STORE, AND MEANS FOR ENABLING SAID PERMANENT AND TEMPORARY STORES ALTERNATIVELY. 